Can Your Multivitamin Help You Slim Down?

There’s still no magic pill for weight loss, but taking a multivitamin might be the secret to a slimmer you.

In a new study of more than 85 obese women in China, those who took a multivitamin (with 29 vitamins and minerals, much like a “one-a-day” you find on store shelves), while continuing to eat their normal diets, lost an average of about three and a half pounds over six months. Those who took a placebo lost nothing.

The findings, reported in February 2010 in the International Journal of Obesity, add to a growing field of research that links vitamins and minerals to weight loss. A study published in 2008 in the British Journal of Nutrition, for example, found that dieting obese men and women who took a multivitamin and mineral supplement lost the same amount of weight as dieters who took a placebo during a 15-week calorie-restricted eating plan. But the female supplement-takers reported feeling less hungry, said lead author Angelo Tremblay, Ph.D., an obesity researcher at Laval University in Quebec City. Being less hungry might make it easier to keep the weight off, says Tremblay.

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Scientists don’t yet know exactly which vitamins and minerals have the biggest influence over appetite and weight control. Calcium seems to help: a number of clinical trials have shown that consuming 1,200 milligrams of calcium a day can boost weight loss in dieters by up to 60 percent, possibly by binding to fat in the gastrointestinal tract, which reduces how much fat the body absorbs. The weight-loss benefits of calcium supplements, however, appear to work best for people who aren’t already getting enough of the mineral. But other nutrients seem to be helpful, too: women in the Chinese study who took multivitamins lost more weight than those who took a supplement that contained only calcium—in the same amount provided by the multivitamin.

One plausible theory as to why multivitamins might help promote weight loss, suggests Tremblay, is that when your body is low on vitamins and minerals, your appetite fires up—prompting you to eat more to replenish the nutrients you’re missing. By staying topped off with nutrients, on the other hand, it may be possible to keep a runaway appetite under control.

Nutrition experts say it’s best to get nutrients from food, but when dieters cut back on calories they are more likely to miss the mark on some nutritional requirements. So although a supplement on its own won’t melt the pounds away, it can help ensure that vitamin and mineral deficiencies aren’t contributing to extra weight.